Re: [PLUG] Puzzling confirmation request

[Charlie Li <ml+PLUG@vishwin.info>]

K.S. Bhaskar wrote:
> I just received a “confirmation request” that starts:
> 
> Your membership in the mailing list plug has been disabled due to
> excessive bounces The last bounce received from you was dated
> 12-Jun-2019.  You will not get any more messages from this list until
> you re-enable your membership.  You will receive 3 more reminders like
> this before your membership in the list is deleted.
> 
> To re-enable your membership, you can simply respond to this message
> (leaving the Subject: line intact), or visit the confirmation page at
> 
> <…snip…>
> 
> Any idea what's going on? Thank you very much.
> 
I suspect this has to do with my posts after I published a DMARC policy
of p=reject on this mail domain.

The Mailman 2 instance this list uses is too old to support any form of
DMARC mitigation (unlike rsk's lists), so anyone posting from a p=reject
domain, particularly Yahoo and AOL, will not have their posts
distributed to every list member that has delivery enabled. This is
because DMARC verifies alignment of all of the From: domain with the
sending MTA, DKIM and SPF (the latter two can pass yet DMARC can still
fail due to misalignment). Unfortunately, mailing lists' regular
operation change the header sequence such that the From: domain doesn't
align with the actual sender's MTA, but rather the mailing list's. This
is a well-known issue [0].

I've temporarily changed my DMARC policy on this domain to p=quarantine
to hopefully prevent further bouncing (although my post may end up in
spam/junk), but still informs of any broken setups I may encounter.

[0] https://en.wikipedia.org/wiki/DMARC#Mailing_lists

-- 
Charlie "DMARC broke the internet, not that magazine cover" Li

(This email address is for mailing list use only; replace local-part
with vishwin for off-list communication)

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